When a semiconductor device such as a metal-oxide-semiconductor field-effect transistor (MOSFET) is scaled down through various technology nodes (e.g., 45 nm, 32 nm, 22 nm, and beyond), device packing density and device performance are challenged by device layout and isolation. In order to avoid leakage between neighboring devices, the following approaches have been applied in standard cell layout design. For example, the standard cell layout adopts an isolated active region island to separate the source of one operational device and the drain of the other operational device, and dummy gate structures of the same type as the operational devices are formed on isolation regions to improve pattern density. As another example, the active region is extended under the dummy gate structures of the same type of as the operational devices to enlarge the epi material of the source and drain regions thereby improving device performance. Although these approaches have been satisfactory for its intended purpose, they have not been satisfactory in all respects.